Light-Driven Paramagnetic Tags for Efficient Pseudocontact Shifts Measurements in Protein NMR Spectroscopy

Pseudocontact shifts (PCSs) are essential for studies of protein structures and dynamics. However, structural calculations typically require multiple tags or labeling at multiple sites, which can be both time-consuming and expensive. In this study, we demonstrate that two independent sets of PCSs can be obtained using an azobenzene-based paramagnetic probe. Upon photoisomerization, the magnetic field around the protein is redistributed, resulting in a distinct NMR spectrum and enabling the acquisition of a new set of structural constraints. This light-driven spatial motion of the paramagnetic center eliminates the need for additional mutations or chemical activators to induce magnetic transitions, paving the way for the development of tensor-switchable paramagnetic tags.